The invention relates to means for measuring the relative humidity and in particular to improvements in psychrometric hygrometers.
Psychrometric hygrometers are the most common means for the determination of relative humidities. The relative humidity is derived from the difference between the dry-bulb and web-bulb temperatures. In currently available psychrometric hygrometers the wet-bulb temperature is obtained by the evaporation of a thin layer of water from a thermometer bulb. This requires means such as wicks for spreading a thin layer of water over a thermometer bulb. In addition, means are required to induce air movements around the wet-bulb. This requires fans or blowers, or rapid movements of the wet thermometer through the surrounding air. The present invention consists of a psychrometric hygrometer which provides a wet-bulb temperature without means for spreading surface water and without induced air movements. It utilizes the evaporation of water from a semi-permeable container rather than from surface water layers. A relatively large surfacevolume container ratio induces a wet-bulb temperature without induced air movements. A detailed description of the invention is given in the Detailed Description section.